Use of compounds which absorb and/or fluoresce in the IR region as markers for liquids

ABSTRACT

Use of compounds from the class of the phthalocyanines, naphthalocyanines, nickel dithiolene complexes, aminium compounds of aromatic amines, methine dyes or azulenesquaric acid dyes which have their absorption maximum in the range from 600 to 1,200 nm and/or a fluorescence maximum in the range from 620 to 1,200 nm, as markers for liquids, a process for detecting markers in liquids, and a detector suitable for this purpose.

This application is a continuation of application Ser. No. 08/844,861,filed on Apr. 23, 1997, now U.S. Pat. No. 5,804,447.

The present invention relates to the use of compounds from the class ofmetal-free or metal-containing phthalocyanines, metal-free ormetal-containing naphthalocyanines, nickel dithiolene complexes, aminiumcompounds of aromatic amines, methine dyes or azulenesquaric acid dyeswhich have their absorption maximum in the range from 600 to 1,200 nmand/or a fluorescence maximum in the range from 620 to 1,200 nm, asmarkers (tracers) for liquids, to a method for detecting markers inliquids, and to a detector suitable for this purpose.

It is frequently necessary to mark liquids in order subsequently, forexample when they are used, to re-detect the thus-marked liquids bymeans of suitable methods.

For example, heating oil can be differentiated from diesel oil in thisway.

It is an object of the present invention to provide suitable compoundswhich are suitable as markers. The markers should have sufficientlystrong absorption and/or fluorescence in the near infrared, so thatdetection of the absorption by means of conventional photometers whichare sensitive in this range and/or of the fluorescence by means ofconventional instruments after excitation with a suitable radiationsource is possible.

We have found that this object is achieved by the compounds described ingreater detail at the outset.

Metal-containing phthalocyanines or naphthalocynanines generally containlithium (twice), magnesium, zinc, copper, nickel, VO, TiO or AlCl as thecentral atom.

Suitable phthalocyanines have, for example, the formula Ia ##STR1##where Me¹ is two hydrogen atoms, two lithium atoms or magnesium, zinc,copper, nickel, VO, TiO, AlCl or Si(OH)₂, at least 4 of the radicals R¹to R¹⁶, independently of one another, have the formula W-X¹ in which Wis a chemical bond, sulfur, imino, C₁ -C₄ -alkylimino or phenylimino,and X¹ is C₁ -C₂₀ -alkyl, which may be interrupted by from 1 to 4 oxygenatoms in ether function or substituted by phenyl, or are adamantyl orsubstituted or unsubstituted phenyl, and

any remaining radicals R¹ to R¹⁶ are hydrogen, halogen, hydroxysulfonylor C₁ -C₄ -dialkylsulfamoyl.

Other suitable phthalocyanines have, for example, the formula Ib##STR2## where R¹⁷ and R¹⁸ or R¹⁸ and R¹⁹ or R¹⁹ and R²⁰ together ineach case have the formula X² -C₂ H₄ -X³, in which one of the tworadicals X¹ and X³ is oxygen and the other is imino or C₁ -C₄-alkylimino, and

R¹⁹ and R²⁰ or R¹⁷ and R²⁰ or R¹⁷ and Re, independently of one another,are in each case hydrogen or halogen, and

Me¹ is as defined above.

Suitable naphthalocyanines have, for example, the formula II ##STR3##where Y¹, Y², Y³, Y⁴, Y⁵, Y⁶, Y⁷ and Y⁸, independently of one another,are each hydrogen, hydroxyl, C₁ -C₂₀ -alkyl or C₁ -C₂₀ -alkoxy, wherethe alkyl groups may each be interrupted by from 1 to 4 oxygen atoms inether function and may be substituted by phenyl,

Y⁹, Y¹⁰, Y¹¹ and Y¹², independently of one another, are each hydrogen,C₁ -C₂₀ -alkyl or C₁ -C₂₀ -alkoxy, where the alkyl groups may each beinterrupted by from 1 to 4 oxygen atoms in ether function, or arehalogen, hydroxysulfonyl or C₁ -C₄ -dialkylsulfamoyl, and

Me² is two hydrogen atoms, two lithium atoms, magnesium, zinc, copper,nickel, VO, TiO, AlCl or ##STR4## where Y¹⁷ and Y¹⁸, independently ofone another, are each hydroxyl, C₁ -C₂₀ -alkoxy, C₁ -C₂₀ -alkyl, C₂ -C₂₀-alkenyl, C₃ -C₂₀ -alkenyloxy or ##STR5## in which Y¹⁹ is C₁ -C₂₀-alkyl, C₂ -C₂₀ -alkenyl or C₄ -C₂₀ -alkadienyl and Y²⁰ and Y²¹,independently of one another, are each C₁ -C₁₂ -alkyl, C₂ -C₁₂ -alkenylor as defined for OY¹⁹ above.

Of particular interest here are naphthalocyanines of the formula II inwhich at least one of Y¹ to Y⁸ is not hydrogen.

Suitable nickel dithiolene complexes have, for example, the formula III##STR6## where L¹, L², L³ and L⁴, independently of one another, are eachC₁ -C₂₀ -alkyl, which may be interrupted by from 1 to 4 oxygen atoms inether function, phenyl, C₁ -C₂₀ -alkylphenyl, C₁ -C₂₀ -alkoxyphenyl,where the alkyl groups may each be interrupted by from 1 to 4 oxygenatoms in ether function, or L¹ and L² and/or L³ and L¹ in each casetogether are ##STR7##

Suitable aminium compounds have, for example, the formula IV ##STR8##where Z¹, Z², Z³ and Z⁴, independently of one another, are each C₁ -C₂₀-alkyl, which may be interrupted by from 1 to 4 oxygen atoms in etherfunction, C₁ -C₂₀ -alkanoyl or ##STR9## where Z⁶ is hydrogen, C₁ -C₂₀-alkyl, which may be interrupted by from 1 to 4 oxygen atoms in etherfunction, or C₁ -C₂₀ -alkanoyl, Z⁷ is hydrogen or C₁ -C₂₀ -alkyl, whichmay be interrupted by from 1 to 4 oxygen atoms in ether function, and Z⁸is hydrogen, C₁ -C₂₀ -alkyl, which may be interrupted by from 1 to 4oxygen atoms in ether function, or halogen, and

An⁸ is the equivalent of an anion.

Suitable methine dyes have, for example, the formula V ##STR10## inwhich the rings A and B, independently of one another, may each bebenzo-fused and/or substituted,

E¹ and E², independently of one another, are each oxygen, sulfur, imino,--C(CH₃)₂ -- or --CH═CH--,

D is ##STR11## where E³ is hydrogen, C₁ -C₆ -alkyl, chlorine or bromineand E⁴ is hydrogen or C₁ -C₆ -alkyl,

Q¹ and Q², independently of one another, are each phenyl,

C₅ -C₇ -cycloalkyl, C₁ -C₁₂ -alkyl, which may be interrupted by from 1to 3 oxygen atoms in ether function and may be substituted by hydroxyl,chlorine, bromine, carboxyl, C₁ -C₄ -alkoxycarbonyl, acryloyloxy,methacryloyloxy, hydroxysulfonyl, C₁ -C₇ -alkanoylamino, C₁ -C₆-alkylcarbamoyl, C₁ -C₆ -alkylcarbamoyloxy or G.sup.⊖ (K)₃, where G isnitrogen or phosphorus and K is phenyl, C₅ -C₇ -cycloalkyl or C₁ -C₁₂-alkyl,

An.sup.⊖ is the equivalent of an anion, and

n is 1, 2 or 3.

Suitable azulenesquaric acid dyes have, for example, the formula VI##STR12## where J is C₁ -C₁₂ -alkylene,

T¹ is hydrogen, halogen, amino, hydroxyl, C₁ -C₁₂ -alkoxy, phenyl,substituted phenyl, carboxyl, C₁ C₁₂ -alkoxycarbonyl, cyano, -NT⁷-CO-T⁶, -CO-NT⁶ T⁷ or -O-CO-NT⁶ T⁷, where T⁶ and T⁷, independently ofone another, are each hydrogen, C₁ -C₁₂ -alkyl, C₅ -C₇ -cycloalkyl,phenyl, 2,2,6,6-tetramethylpiperidin-4-yl or cyclohexylaminocarbonyl,and

T², T³, T⁴ and T⁵, independently of one another, are each hydrogen or C₁-C₁₂ -alkyl, which may be substituted by halogen, amino, C₁ -C₁₂-alkoxy, phenyl, substituted phenyl, carboxyl, C₁ -C₁₂ -alkoxycarbonylor cyano,

with the proviso that, if T⁵ is hydrogen, the ring positions of thesubstituents J-T¹ and T⁴ within an azulene ring may also be exchangedfor one another on one or both azulene rings.

All the alkyl, alkylene and alkenyl radicals occurring in the aboveformulae may be either straight-chain or branched.

In the formulae Ia, II, III and IV, suitable C₁ -C₂₀ -alkyl radicals,which may be interrupted by from 1 to 4 oxygen atoms in ether function,are, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl,secbutyl, tert-butyl, pentyl, isopentyl, neopentyl, tertpentyl, hexyl,2-methylpentyl, heptyl, octyl, 2-ethylhexyl, isooctyl, nonyl, isononyl,decyl, isodecyl, undecyl, dodecyl, tridecyl, 3,5,5,7-tetramethylnonyl,isotridecyl (the above terms isooctyl, isononyl, isodecyl andisotridecyl are trivial names and originate from the alcohols obtainedfrom the oxo synthesis--cf. in this respect Ullmanns Encyklopadie dertechnischen Chemie, 4th Edition, Volume 7, pages 215-217, and Volume 11,pages 435 and 436), tetradecyl, pentadecyl, hexadecyl, heptadecyl,octadecyl, nonadecyl, eicosyl, 2-methoxyethyl, 2-ethoxyethyl,2-propoxyethyl, 2-isopropoxyethyl, 2-butoxyethyl, 2- and3-methoxypropyl, 2- and 3-ethoxypropyl, 2- and 3-propoxypropyl, 2- and3-butoxypropyl, 2- and 4-methoxybutyl, 2- and 4-ethoxybutyl, 2- and4-propoxybutyl, 2- and 4-butoxybutyl, 3,6-dioxaheptyl, 3,6-dioxaoctyl,4,8-dioxanonyl, 3,7-dioxaoctyl, 3,7-dioxanonyl, 4,7-dioxaoctyl,4,7-dioxanonyl, 4,8-dioxadecyl, 3,6,8-trioxadecyl, 3,6,9-trioxaundecyl,3,6,9,12-tetraoxatridecyl and 3,6,9,12-tetraoxatetradecyl.

In the formulae I and II, suitable phenyl-substituted C₁ -C₂₀ -alkylradicals are, for example, benzyl and 1- and 2-phenylethyl.

In the formulae II, III and IV, suitable C₁ C₂₀ -alkoxy radicals, whichmay be interrupted by from 1 to 4 oxygen atoms in ether function, are,for example, methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy,pentoxy, hexyloxy, heptyloxy, octyloxy, 2-ethylhexyloxy, isooctyloxy,nonyloxy, isononyloxy, decyloxy, iso-decyloxy, undecyloxy, dodecyloxy,tridecyloxy, isotridecyloxy, tetradecyloxy, pentadecyloxy, hexadecyloxy,heptadecyloxy, octadecyloxy, nonadecyloxy, eicosyloxy, 2-methoxyethoxy,2-ethoxyethoxy, 2-propoxyethoxy, 2-isopropoxyethoxy, 2-butoxyethoxy, 2-and 3-methoxypropoxy, 2- and 3-ethoxypropoxy, 2- and 3-propoxypropoxy,2- and 3-butoxypropoxy, 2- and 4-methoxybutoxy, 2- and 4-ethoxybutoxy,2- and 4-propoxybutoxy, 2- and 4-butoxybutoxy, 3,6-dioxaheptyloxy,3,6-dioxaoctyloxy, 4,8-dioxanonyloxy, 3,7-dioxaoctyloxy,3,7-dioxanonyloxy, 4,7-dioxaoctyloxy, 4,7-dioxanonyloxy,4,8-dioxadecyloxy, 3,6,8-trioxadecyloxy, 3,6,9-trioxaundecyloxy,3,6,9,12-tetraoxatridecyloxy and 3,6,9, 12-tetraoxatetradecyloxy.

In the formula II, suitable phenyl-substituted C₁ -C₂₀ -alkoxy radicalsare, for example, benzyloxy and 1- and 2-phenylethoxy.

In the formulae Ia, III and VI, suitable substituted phenyl radicalsare, for example, phenyl which is substituted by C₁ -C₆ -alkyl, C₁ -C₆-alkoxy, hydroxyl or halogen. In general, there may be from 1 to 3substituents.

Halogen in the formulae Ib, II, IV and VI is, for example, fluorine,chlorine or bromine.

The radicals W in the formula Ia and X² and X³ in the formula Ib are,for example, methylimino, ethylimino, propylimino, isopropylimino orbutylimino.

The radicals R¹ to R¹⁶ in the formula Ia and Y⁹ to Y¹² in the formula IIare, for example, dimethylsulfamoyl, diethylsulfamoyl,dipropylsulfamoyl, dibutylsulfamoyl or N-methyl-N-ethylsulfamoyl.

C₂ -C₂₀ -alkenyl and C₁ -C₂₀ -alkandienyl in the formula II are, forexample, vinyl, allyl, prop-1-en-1-yl, methallyl, ethallyl,but-3-en-1-yl, pentenyl, pentadienyl, hexadienyl, 3, 7-dimethylocta-1,6-dien-1-yl, undec-10-en-1-yl, 6, 10-dimethylundeca-5, 9-dien-2-yl,octadec-9-en-1-yl, octadeca-9,12-dien-1-yl,3,7,11,15-tetramethylhexadec-1-en-3-yl or eicos-9-en-1-yl.

C₃ -C₂₀ -alkenyloxy in the formula II is, for example, allyloxy,methallyloxy, but-3-en-1-yloxy, undec-10-en-1-yloxy,octadec-9-en-1-yloxy or eicos-9-en-1-yloxy.

Z⁶ in the formula IV is, for example, formyl, acetyl, propionyl,butyryl, isobutyryl, pentanoyl, hexanoyl, heptanoyl, octanoyl or2-ethylhexanoyl.

If the rings A and/or B in the formula V are substituted, suitablesubstituents are, for example, C₁ -C₆ -alkyl, phenyl-C₁ -C₆ -alkoxy,phenoxy, halogen, hydroxyl, amino, C₁ -C₆ -mono- or dialkylamino orcyano. The rings are generally monosubstituted to trisubstituted.

The radicals E³, E⁴, Q¹ and Q² in the formula V are, for example,methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, pentyl,isopentyl, neopentyl, tert-pentyl or hexyl.

The radicals Q¹ and Q² are furthermore, for example, hexyl,2-methylpentyl, heptyl, octyl, 2-ethylhexyl, isooctyl, nonyl, isononyl,decyl, isodecyl, undecyl, dodecyl, cyclopentyl, cyclohexyl,2-methoxyethyl, 2-ethoxyethyl, 2- or 3-methoxypropyl, 2- or3-ethoxypropyl, 2-hydroxyethyl, 2- or 3-hydroxypropyl, 2-chloroethyl,2-bromoethyl, 2- or 3-chloropropyl, 2- or 3-bromopropyl, 2-carboxyethyl,2- or 3-carboxypropyl, 2-methoxycarbonylethyl, 2-ethoxycarbonylethyl, 2-or 3-methoxycarbonylpropyl, 2- or 3-ethoxycarbonylpropyl,2-acryloyloxyethyl, 2- or 3-acryloyloxypropyl, 2-methacryloyloxyethyl,2- or 3-methacryloyloxypropyl, 2-hydroxysulfonylethyl, 2- or3-hydroxysulfonylpropyl, 2-acetylaminoethyl, 2- or 3-acetylaminopropyl,2-methylcarbamoylethyl, 2-ethylcarbamoylethyl, 2- or3-methylcarbamoylpropyl, 2- or 3-ethylcarbamoylpropyl,2-methylcarbamoyloxyethyl, 2-ethylcarbamoyloxyethyl, 2- or3-methylcarbamoyloxypropyl, 2- or 3-ethylcarbamoyloxypropyl, 2-(trimethylammonium) ethyl, 2-(triethylammonium) ethyl, 2- or3-(trimethylammonium)propyl, 2- or 3-(triethylammonium)propyl,2-(triphenylphosphonium)ethyl or 2- or 3-(triphenylphosphonium)propyl.

An.sup.⊖ in the formulae IV and V is derived, for example, from anionsof organic or inorganic acids. Particular preference is given to, forexample, methanesulfonate, 4-methylbenzenesulfonate, acetate,trifluoroacetate, heptafluorobutyrate, chloride, bromide, iodide,perchlorate, tetrafluoroborate, nitrate, hexafluorophosphate andtetraphenylborate.

The radicals J in the formula VI are, for example, methylene, ethylene,1,2- or 1,3-propylene, 1,2-, 1,3-, 2,3- or 1,4-butylene, pentamethylene,hexamethylene, heptamethylene, octamethylene, nonamethylene,decamethylene, undecamethylene or dodecamethylene.

The radicals T², T³ , T⁴ and T⁵ in the formula VI are, for example,methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl,tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, 2-methylbutyl,hexyl, 2-methylpentyl, heptyl, octyl, 2-ethylhexyl, isooctyl, nonyl,isononyl, decyl, undecyl, dodecyl, fluoromethyl, chloromethyl,difluoromethyl, trifluoromethyl, trichloromethyl, 2-fluoroethyl,2-chloroethyl, 2-bromomethyl, 1,1,1-trifluoroethyl, heptafluoropropyl,4-chlorobutyl, 5-fluoropentyl, 6-chlorohexyl, cyanomethyl, 2-cyanoethyl,3-cyanopropyl, 2-cyanobutyl, 4-cyanobutyl, 5-cyanopentyl, 6-cyanohexyl,2-aminoethyl, 2-aminopropyl, 3-aminopropyl, 2-aminobutyl, 4-aminobutyl,5-aminopentyl, 6-aminohexyl, 2-hydroxyethyl, 2-hydroxypropyl,3-hydroxypropyl, 2-hydroxybutyl, 4-hydroxybutyl, 5-hydroxypentyl,6-hydroxyhexyl, 2-methoxyethyl, 2-ethoxyethyl, 2-propoxyethyl,2-isopropoxyethyl, 2-butoxyethyl, 2-methoxypropyl, 2-ethoxypropyl,3-ethoxypropyl, 4-ethoxybutyl, 4-isopropoxybutyl, 5-ethoxypentyl,6-methoxyhexyl, benzyl, 1-phenylethyl, 2-phenylethyl, 4-chlorobenzyl,4-methoxybenzyl, 2-(4-methylphenyl)ethyl, carboxymethyl, 2-carboxyethyl,3-carboxypropyl, 4-carboxybutyl, 5-carboxypentyl, 6-carboxyhexyl,methoxycarbonylmethyl, ethoxycarbonylmethyl, 2-methoxycarbonylethyl,2-ethoxycarbonylethyl, 3-methoxycarbonylpropyl, 3-ethoxycarbonylpropyl,4-methoxycarbonylbutyl, 4-ethoxycarbonylbutyl, 5-methoxycarbonylpentyl,5-ethoxycarbonylpentyl, 6-methoxycarbonylhexyl or 6-ethoxycarbonylhexyl.

T¹ in the formula VI is, for example, methoxycarbonyl, ethoxycarbonyl,propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, isobutoxycarbonyl,sec-butoxycarbonyl, tert-butoxycarbonyl, pentoxycarbonyl,isopentoxycarbonyl, neopentoxycarbonyl, tert-pentoxycarbonyl,hexyloxycarbonyl, heptyloxycarbonyl, octyloxycarbonyl,isooctyloxycarbonyl, nonyloxycarbonyl, isononyloxycarbonyl,decyloxycarbonyl, isodecyloxycarbonyl, undecyloxycarbonyl,dodecyloxycarbonyl, methoxy, ethoxy, propoxy, isopropoxy, butoxy,isobutoxy, pentoxy, hexyloxy, acetylamino, carbamoyl, mono- ordimethylcarbamoyl, mono- or diethylcarbamoyl, monocyclohexylcarbonyl,phenylcarbamoyl, dimethylcarbamoyloxy or diethylcarbamoyloxy.

Preference is given to the use according to the invention of compoundsoriginating from the class of metal-free or metal-containingnaphthalocyanines.

Emphasis should be placed on the use according to the invention ofnaphthalocyanines of the formula IIa ##STR13## where Y¹, Y², Y³, Y⁴, Y⁵,Y⁶, Y⁷ and Y⁸, independently of one another, are each hydrogen,hydroxyl, C₁ -C₄ -alkyl or C₁ -C₂₀ -alkoxy, and

Me² is two hydrogen atoms, two lithium atoms, magnesium, zinc, copper,nickel, VO, AlCl or ##STR14## where R¹⁹ is C₁ -C₁₃ -alkyl or C₁₀ -C₂₀-alkadienyl and Y²⁰ and Y²¹, independently of one another, are each C₁-C₁₃ -alkyl or C₂ -C₄ -alkenyl.

Particular emphasis should be placed on the use according to theinvention of naphthalocyanines of the formula IIa, where Y¹, Y², Y³, Y⁴,Y⁵, Y⁶, Y⁷ and Y⁸, independently of one another, are each hydroxyl or C₁-C₂₀ -alkoxy, in particular C₁ -C₁₀ -alkoxy. The alkoxy radicals heremay be identical or different.

Particular emphasis should furthermore be placed on the use according tothe invention of naphthalocyanines of the formula IIa where Me² is twohydrogen atoms.

Emphasis should furthermore be placed on the use according to theinvention of nickel dithiolene complexes of the formula III, where L¹,L², L³ and L⁴, independently of one another, are each phenyl, C₁ -C₂₀-alkylphenyl, C₁ -C₂₀ -alkoxyphenyl or hydroxyl- and C₁ -C₂₀ -alkylsubstituted phenyl, or L¹ and L² and L³ and L⁴ are in each case together##STR15##

Particular emphasis should furthermore be placed on the use according tothe invention of nickel dithiolene complexes of the formula III where L¹and L⁴ are each phenyl and L² and L⁴ are each 4-[C₂ H₅ -C(CH₃)₂ ]-C₆ H₄.

The phthalocyanines of the formula Ia are known per se and aredescribed, for example, in DE-B-1 073 739 or EP-A-155 780 or can beobtained by methods known per se, as used in the preparation ofphthalocyanines or naphthalocyanines and as described, for example, inF. H. Moser, A. L. Thomas, "The Phthalocyanines", CRC Press, Boca Rota,Fla., 1983, or J. Am. Chem. Soc. 106 (1984), 7404 to 7410. Thephthalocyanines of the formula Ib are likewise known per se and aredescribed, for example, in EP-A-155 780 or can be obtained by the aboveprior-art methods (Moser, J. Am. Chem. Soc.).

The naphthalocyanines of the formula II are likewise known per se andare described, for example, in EP-A-336 213, EP-A-358 080,GB-A-2,168,372 or GB-A-2,200,650, or can be obtained by the aboveprior-art methods (Moser, J. Am. Chem. Soc.).

The nickel dithiolene complexes of the formula III are likewise knownper se and are described, for example, in EP-A-192 215.

The aminium compounds of the formula IV are likewise known per se andare described, for example, in U.S. Pat. No. 3,484,467 or can beobtained by the methods mentioned therein.

The methine dyes of the formula V are likewise known per se and aredescribed, for example, in EP-A-464 543 or can be obtained by themethods described therein.

The azulenesquaric acid dyes of the formula VI are likewise known per seand are described, for example, in EP-A-310 080 or U.S. Pat. No.4,990,649 or can be obtained by the methods described therein.

Suitable solvents which can be marked according to the invention bymeans of the compounds described in greater detail above are, inparticular, organic liquids, for example alcohols, such as methanol,ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol,pentanol, isopentanol, neopentanol and hexanol, glycols, such as1,2-ethylene glycol, 1,2- and 1,3-propylene glycol, 1,2-, 2,3- and1,4-butylene glycol, di- and triethylene glycol and di- and tripropyleneglycol, ethers, such as methyl tert-butyl ether, 1,2-ethylene glycolmono- and dimethyl ether, 1,2-ethylene glycol mono- and diethyl ether,3-methoxypropanol, 3-isopropoxypropanol, tetrahydrofuran and dioxane,ketones, such as acetone, methyl ethyl ketone and diacetone alcohol,esters, such as methyl acetate, ethyl acetate, propyl acetate and butylacetate, aliphatic and aromatic hydrocarbons, such as pentane, hexane,heptane, octane, isooctane, petroleum ether, toluene, xylene,ethylbenzene, tetralin, decalin, dimethylnaphthalene, white spirit,mineral oil, such as gasoline, kerosene, diesel oil and heating oil,natural oils, such as olive oil, soya oil and sunflower oil, and naturalor synthetic engine oils, hydraulic oils and transmission oils, forexample vehicle engine oil and sewing machine oil, and brake fluids.

The abovementioned compounds are particularly advantageously used formarking mineral oils in which labeling is simultaneously required, forexample for tax reasons. In order to keep costs of the labeling low, theusual aim is to use very dilutable dyes for the coloring. However, evendyes of high tinctorial strength cannot be detected purely visually inhigh dilution in mineral oils.

For this reason, it is of particular advantage to use markers which havetheir absorption maximum in the range from 600 to 1,200 nm and/orfluoresce in the range from 620 to 1,200 nm, since they can easily bedetected using suitable instruments.

For labeling liquids, but in particular mineral oil, the abovementionedcompounds are generally used in the form of solutions. Suitable solventsare preferably aromatic hydrocarbons, such as toluene and xylene. Inorder to avoid any excessively high viscosity of the resultantsolutions, a concentration of the compound which absorbs and/orfluoresces in the IR of from 2 to 50% by weight, based on the solution,is generally selected.

The present invention furthermore provides a process for detectingmarkers in liquids, which comprises detecting the marker from itsfluorescence in the NIR (near infrared) spectral region.

The fluorescence of the markers present in the liquids is advantageouslyexcited by means of a semiconductor laser or a semiconductor diode. Itis particularly favorable to use a semiconductor laser or asemiconductor diode having a wavelength of maximum emission in thespectral range from λ_(max) -100 nm to λ_(max) +20 nm, where λ_(max) isthe wavelength of the absorption maximum of the marker. The wavelengthof maximum emission is in the range from 620 to 1,200 nm.

The fluorescence light produced in this way is advantageously detectedby means of a semiconductor detector, in particular a silicon photodiodeor a germanium photodiode.

Detection is particularly advantageous if the detector is preceded by aninterference filter and/or a cut-off filter (with a short-wavetransmission cut-off limit in the range from λ_(max) to λ_(max) +80 nm)and/or a polarizer.

The abovementioned compounds make it very simple to detect markedliquids, even if the marker substances are only present in aconcentration of approximately 0.1 ppm (detection by absorption) orapproximately 5 ppb (detection by fluorescence).

The present invention furthermore provides an instrument for carryingout the process according to the invention (=detector), the detectorcomprising an NIR light source (semiconductor laser or semiconductordiode), one or more optical filters, an NIR polarizer and aphotodetector (silicon photodiode or germanium photodiode) and, ifdesired, optical fibers or optical fiber bundles.

The examples below are intended to illustrate the invention in greaterdetail.

General procedure for detecting the markers.

I. Detection by absorption in the IR region

EXAMPLE 1

Sufficient dye of the formula ##STR16## was dissolved in diesel fuel togive a solution containing 1,000 ppm of dye.

This solution was diluted further in steps, and its absorption in theNIR region measured against a pure diesel fuel using a commerciallyavailable spectrometer (1 cm cell).

    ______________________________________                                        Dye content in           Absorption                                                                     diesel fuel [ppm] Absorption maximum [nm]           ______________________________________                                        100            >>3       --                                                     50 3.05 844.0                                                                 20 2.81 854.0                                                                 10 2.10 860.4                                                                  1 0.27 860.0                                                               ______________________________________                                    

Similarly favorable results are achieved when naphthalocyanines of theabove formula (where R=n-C₅ H₁₁ or n-C₁₂ H₂₅) or the dyes listed beloware used for the marking.

    __________________________________________________________________________    Dye 2                                                                           Hexadecaphenylthiocopper phthalocyanine                                       Dye 3                                                                         Tetradecaphenylthiocopper phtahlocyanine                                      Dye 4                                                                         Tetradecadodecylthiocopper phthalocyanine                                     Dye 5                                                                         #STR17##                                                                       - Dye 6                                                                      Hexadeca(4 tert-butylphenylthio)copper phthalocyanine                         Dye 7                                                                         NcSi[--O--Si(CH.sub.3).sub.2 --O--C.sub.12 H.sub.25 ].sub.2                   Dye 8                                                                          -                                                                            #STR18##                                                                       - Dye 9                                                                       -                                                                            #STR19##                                                                       - Dye 10                                                                      -                                                                            #STR20##                                                                       - Dyes 11 to 15                                                               -                                                                            #STR21##                                                                    __________________________________________________________________________    Dye                                                                             No. L.sup.1 L.sup.2 L.sup.3 L.sup.4                                         __________________________________________________________________________      11                                                                                                                  C.sub.6 H.sub.5                                                               C.sub.6 H.sub.5                          - 12                                                                                                               C.sub.6 H.sub.5                                                               C.sub.6 H.sub.5                          - 13 C.sub.6 H.sub.5 C.sub.6 H.sub.5 C.sub.6 H.sub.5 C.sub.6 H.sub.5                                               - 14                                                                          C.sub.6 H.sub.5                                                               C.sub.6 H.sub.5                          - 15                                                                                               #STR28##                                                                      #STR29##                                              __________________________________________________________________________      Dyes 15 to 18                                                                  -                                                                            #STR30##                                                                    __________________________________________________________________________    Dye No.       Z            An.sup.⊖                                   __________________________________________________________________________      16 C.sub.4 H.sub.9 NO.sub.3.sup.⊖                                     17 C.sub.2 H.sub.5 NO.sub.3.sup.⊖                                     18 C.sub.4 H.sub.9 BF.sub.4.sup.⊖                                   __________________________________________________________________________    Dyes 19 to 23                                                                    -                                                                            #STR31##                                                                    __________________________________________________________________________    Dye No.                                                                             Q.sup.1    Q.sup.2    Q.sup.3                                                                          Q.sup.4                                                                          An.sup.⊖                            __________________________________________________________________________      19 CH.sub.3 CH.sub.3 Cl Cl I.sup.⊖                                    20 CH.sub.3 CH.sub.3 H H I.sup.⊖                                       - 21                                                                                                           #STR32##                                                                      H H I.sup.⊖                          - 22                                                                                                           #STR34##                                                                      H H ClO.sub.4.sup.⊖                  - 23 C.sub.3 H.sub.6 SO.sub.3.sup.⊖ C.sub.3 H.sub.6 SO.sub.3 H                                       H H Betain                                  __________________________________________________________________________    Dye 24                                                                          #STR36##                                                                    __________________________________________________________________________

II. Detection by fluorescence in the NIR region

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows the diagrammatic structure of the detector.

The marker fluorescence is excited using the emission from a commercialsemiconductor diode laser. The parallel laser beam is shone onto thesample in a 1 cm cell. In order to double the excitation intensity, thetransmitted light beam is reflected by a mirror and again shone throughthe sample.

The fluorescence light is imaged by means of optical elements (lenssystem) onto the detector, a silicon photodiode. The light emitted atthe rear is likewise thrown onto the silicon photodiode by a concavemirror.

In order to separate the unwanted light (scattered excitation light)from the fluorescence light, cutoff and/or interference filters and/or apolarizer (NIR polarization foil) are used.

The optimization of the polarizer is selected so that the direction ofmaximum transmission is perpendicular to the polarization plane of theexcitation light.

EXAMPLE 25

Sufficient dye of the formula ##STR37## was dissolved in diesel fuel togive a stock solution containing 219 ppb of dye. Further solutions wereprepared therefrom by dilution with diesel fuel.

These solutions were measured in accordance with general procedure IIusing the following equipment settings.

Excitation: GaAlAs semiconductor diode laser having a wavelength of 813nm; CW output 7 mW.

Filter: Long-pass interference filter 850 nm (Corion). Photodetector:Silicon photodiode having an area of 1 cm² (UDT). The photocurrent wasmeasured using a current/voltage converter (UDT, model 350).

The results are shown in the table below.

    ______________________________________                                                                 Fluorescence                                           Dye content in the Absorbance signal                                          diesel fuel [ppb] at .sub.max (in scale units)                              ______________________________________                                        219            0.05      2366                                                   43.7 0.01 451                                                                 8.75 0.002 106                                                                1.75 0.0004  40                                                               0 0.0  20                                                                   ______________________________________                                    

This gives a lower detection limit for the marker by fluorescence ofabout 5 ppb.

Similarly favorable results are achieved when naphthalocyanines of theabove formula (where R=n-C₅ H₁₁ or n-C₁₂ H₂₅) or the dyes listed beloware used for the marking.

    __________________________________________________________________________      #STR38##                                                                    Dye 26                                                                          Me = 2H                                                                       Dye 27                                                                        Me = Zn                                                                       Dye 28                                                                        Me = AlCl                                                                     Dye 29                                                                        NcSi[--O--Si(CH.sub.3).sub.2 --O--C.sub.12 H.sub.25 ].sub.2                   Dye 30                                                                         -                                                                            #STR39##                                                                       - Dye 31                                                                      -                                                                            #STR40##                                                                       - Dye 32                                                                      -                                                                            #STR41##                                                                       - Dye 33                                                                      -                                                                            #STR42##                                                                       - Dye 34                                                                      -                                                                            #STR43##                                                                       - Dyes 35 to 37                                                               -                                                                            #STR44##                                                                    __________________________________________________________________________    Dye No.       Z            An.sup.⊖                                   __________________________________________________________________________      35 C.sub.4 H.sub.9 NO.sub.3.sup.⊖                                     36 C.sub.2 H.sub.5 NO.sub.3.sup.⊖                                     37 C.sub.4 H.sub.9 BF.sub.4.sup.⊖                                   __________________________________________________________________________    Dyes 38 to 42                                                                    -                                                                            #STR45##                                                                    __________________________________________________________________________    Dye No.                                                                             Q.sup.1    Q.sup.2    Q.sup.3                                                                          Q.sup.4                                                                          An.sup.⊖                            __________________________________________________________________________      38 CH.sub.3 CH.sub.3 Cl Cl I.sup.⊖                                    39 CH.sub.3 CH.sub.3 H H I.sup.⊖                                       - 40                                                                                                           #STR46##                                                                      H H I.sup.⊖                          - 41                                                                                                           #STR48##                                                                      H H ClO.sub.4.sup.⊖                  - 42 C.sub.3 H.sub.6 SO.sub.3.sup.⊖ C.sub.3 H.sub.6 SO.sub.3 H                                       H H Betain                                  __________________________________________________________________________    Dye 43                                                                           -                                                                            #STR50##                                                                    __________________________________________________________________________

We claim:
 1. A method of identifying a liquid comprising the sequentialsteps of:(i) detecting a marker compound in a liquid; and (ii)identifying said liquid based on the identity of said markercompound,wherein said marker compound exhibits an absorption maximum inthe range of 600-1,200 nm and/or a fluorescence maximum in the range of620-1,200 nm, and wherein said marker compound is a compound of FormulaIa, Ib, III, IV, V or VI, ##STR51## where Me¹ is two hydrogen atoms, twolithium atoms or magnesium, zinc, copper, nickel, VO, TiO, AlCl orSi(OH)₂, at least 4 of the radicals R¹ to R¹⁶, independently of oneanother, have the formula W-X¹ in which W is a chemical bond, sulfur,imino, C₁ -C₄ -alkylimino or phonylimino, and X¹ is C₁ -C₂₀ -alkyl,which may be interrupted by from 1 to 4 oxygen atoms in ether functionor substituted by phenyl, or are adamantyl or substituted orunsubstituted phenyl, andany remaining radicals R¹ to R¹⁶ are hydrogen,halogen, hydroxysulfonyl or C₁ -C₄ -dialkylsulfamoyl), ##STR52## whereR¹⁷ and R¹⁸ or R¹⁸ and R¹⁹ or R¹⁹ and R²⁰ together in each case have theformula X² -C₂ H₄ -X³, in which one of the two radicals X² and X³ isoxygen and the other is imino or C₁ -C₄ -alkylimino, and R¹⁹ and R²⁰ orR¹⁷ and R²⁰ or R¹⁷ and R¹⁸, independently of one another, are in eachcase hydrogen or halogen, and Me¹ is as defined above, ##STR53## whereY¹, Y², Y³, Y⁴, Y⁵, Y⁶, Y⁷ and Y⁸, independently of one another, areeach hydrogen, hydroxyl, C₁ -C₂₀ -alkyl or C₁ -C₂₀ -alkoxy, where thealkyl groups may each be interrupted by from 1 to 4 oxygen atoms inether function and may be substituted by phenyl, Y⁹, Y¹⁰, Y¹¹ and Y¹²,independently of one another, are each hydrogen, C₁ -C₂₀ -alkyl or C₁-C₂₀ -alkoxy, where the alkyl groups may each be interrupted by from 1to 4 oxygen atoms in ether function, or are halogen, hydroxysulfonyl orC₁ -C₄ -dialkylsulfamoyl, and Me² is two hydrogen atoms, two lithiumatoms, magnesium, zinc, copper, nickel, VO, TiO, AlCl or ##STR54## whereY¹⁷ and Y¹⁸, independently of one another, are each hydroxyl, C₁ -C₂₀-alkoxy, C₁ -C₂₀ -alkyl, C₂ -C₂₀ -alkenyl, C₃ -C₂₀ -alkenyloxy or##STR55## in which Y¹⁹ is C₁ -C₂₀ -alkyl, C₂ -C₂₀ -alkenyl or C₄ -C₂₀-alkadienyl and Y²⁰ and Y²¹, independently of one another, are each C₁-C₁₂ -alkyl, C₂ -C₁₂ -alkenyl or as defined for OY¹⁹ above, ##STR56##where L₁, L², L³ and L⁴, independently of one another, are each C₁ -C₂₀-alkyl, which may be interrupted by from 1 to 4 oxygen atoms in etherfunction, phenyl, C₁ -C₂₀ -alkylphenyl, C₁ -C₂₀ -alkoxyphenyl, where thealkyl groups may each be interrupted by from 1 to 4 oxygen atoms inether function, or L¹ and L² and/or L³ and L⁴ in each case together are##STR57## where Z¹, Z², Z³ and Z⁴, independently of one another, areeach C₁ -C₂₀ -alkyl, which may be interrupted by from 1 to 4 oxygenatoms in ether function, C₁ -C₂₀ -alkanoyl or ##STR58## where Z⁴ ishydrogen, C₁ -C₂₀ -alkyl, which may be interrupted by from 1 to 4 oxygenatoms in ether function, or C₁ -C₂₀ -alkanoyl, Z⁷ is hydrogen or C₁ -C₂₀-alkyl, which may be interrupted by from 1 to 4 oxygen atoms in etherfunction, and Z⁸ is hydrogen, C₁ -C₂₀ -alkyl, which may be interruptedby from 1 to 4 oxygen atoms in ether function, or halogen, and An.sup.⊖is the equivalent of an anion, ##STR59## in which the rings A and B,independently of one another, may each be benzo-fused and/orsubstituted, E¹ and E², independently of one another, are each oxygen,sulfur, imino, --C(CH₃)₂ -- or --CH═CH--, D is ##STR60## where E³ ishydrogen, C₁ -C₆ -alkyl, chlorine or bromine and E⁴ is hydrogen or C₁-C₆ -alkyl, Q¹ and Q², independently of one another, are each phenyl, C₅-C₇ -cycloalkyl, C₁ -C₁₂ -alkyl, which may be interrupted by from 1 to 3oxygen atoms in ether function and may be substituted by hydroxyl,chlorine, bromine, carboxyl, C₁ -C₄ -alkoxycarbonyl, acryloyloxy,methacryloyloxy, hydroxysulfonyl, C₁ -C₇ -alkanoylamino, C₁ -C₆-alkylcarbamoyl, C₁ -C₆ -alkylcarbamoyloxy or G^(e) (K)₃, where G isnitrogen or phosphorus and K is phenyl, C₅ -C₇ -cycloalkyl or C₁ -C₁₂-alkyl, An.sup.⊖ is the equivalent of an anion, and n is 1, 2 or 3,##STR61## where J is C₁ -C₁₂ -alkylene, T¹ is hydrogen, halogen, amino,hydroxyl, C₁ -C₁₂ -alkoxy, phenyl, substituted phenyl, carboxyl, C₁ -C₁₂-alkoxycarbonyl, cyano, -NT⁷ -CO-T⁶, -CO-NT⁶ T⁷ or -O-CO-NT⁶ T⁷, whereT⁶ and T⁷, independently of one another, are each hydrogen, C₁ -C₁₂-alkyl, C₅ -C₇ -cycloalkyl, phenyl, 2,2,6,6-tetramethylpiperidin-4-yl orcyclohexylaminocarbonyl, and T², T³, T⁴ and T⁵, independently of oneanother, are each hydrogen or C₁ -C₁₂ -alkyl, which may be substitutedby halogen, amino, C₁ -C₁₂ -alkoxy, phenyl, substituted phenyl,carboxyl, C₁ -C₁₂ -alkoxycarbonyl or cyano,with the proviso that, if T⁵is hydrogen, the ring positions of the substituents J-T¹ and T⁴ withinan azulene ring may also be exchanged for one another on one or bothazulene rings.